U.S. Pat. No. 9,193,015 B2 discloses an exemplary component placement device. The placement of such components desirably occurs with high speed and accuracy.
To attain such a high speed, the component pickup unit is moved from the pickup position with a relatively high acceleration. In a similar manner, the component pickup unit is quickly decelerated near the desired position on the substrate or, in other words, is moved with a relatively high negative acceleration. Such high accelerations also occur upon returning to the pickup position. Because of such accelerations, relatively large reactive forces are exerted on the subframe by the component pickup unit. Such reactive forces cause among other things, vibrations and deformations of the machine frame and possible other subframes supported by the machine frame, thus affecting the accuracy with which another component pickup unit can be moved to a desired position. This effect is called dynamic crosstalk, which term is understood to mean the influence of the dynamic behaviour of one component pickup unit on the positioning accuracy of another component pickup unit. Vibrations and deformations of the machine frame may affect other devices in the neighbourhood of the component placement device.
In order to reduce the influence of such reactive forces, it is possible to move the component pickup unit at lower accelerations. However, this will have an adverse effect on the number of components that can be moved per unit time. Another possibility is to make the machine frame much heavier and stiffer, so that the reactive forces can be better absorbed. This will make the component placement device relatively costly to produce and use, however.
According to U.S. Pat. No. 9,193,015 B2, the component placement device includes a machine frame and component pickup units which are movable relative to a respective subframe supported by the machine frame. The component pickup units are movable in a direction of movement. The component placement device includes means for determining the magnitude of a counterforce to be exerted on the subframe substantially in the direction of movement, as well as at least one drive unit for exerting the counterforce determined by the means substantially in the direction of movement on the subframe for the purpose of at least partially counteracting a reactive force exerted on the subframe by the component pickup unit during movement of the component pickup unit in the direction of movement relative to the subframe.
The drive unit of U.S. Pat. No. 9,193,015 B2 includes two parts, whereby the subframe is provided with a first part of the drive unit, while a second part of the drive unit, which cooperates with the first part of the drive unit, is mounted on an auxiliary frame that is freestanding from the machine frame. A disadvantage of the component placement unit according to U.S. Pat. No. 9,193,015 B2 is that it utilizes such an auxiliary freestanding frame.
The size and costs of the auxiliary freestanding frame depends on the number of component pick up units. The costs for such a frame for a single component pick up unit are relatively high. If one common frame is made for all component pick up units, the costs per component pick up are lower but only if each component pick up unit includes such a drive unit. The flexibility of the known component placement unit is thereof low.